Internal reinforcement method of upgrading progressive collapse resistance of reinforced concrete framed system

Abstract

The invention discloses a mitigating method comprising a reinforcement scheme for upgrading progressive collapse resistance of a floor system prone to column failure, the method comprising adding a plurality of diagonal steel bars in the vicinity of a potentially failed column, thereby developing a post-tensioning axial compressive force in the floor beams of the floor system. Steel bars or links left over from construction sites as well as used steel bars and structural steel sections from demolition sites are used/reused as the plurality of diagonal steel bars to mitigate progressive collapse of framed structures under potential column failure. Depending on a number and configuration of the added diagonal steel bars, the percentage increases in the beam axial compressive force, catenary action capacity, total dissipated energy, and maximum vertical displacement by the mitigated floor system ranged between 104.5% and 161.3%, 105.1% and 180.5%, 115% and 241.8%, and 106% and 167.4%, respectively.

The invention claimed is: 
     
       1. A method of enhancing progressive collapse resistance of a reinforced concrete floor system, the method comprising:
 adding a plurality of diagonal top and bottom reinforcing bars within floor slab panels in a vicinity of a potentially failed column;
 wherein the added diagonal top and bottom reinforcing bars connect orthogonal floor beams bridging over the potentially failed column and act as links/ties between the orthogonal floor beams when the column fails, and each of the diagonal reinforcing bars comprises a length not exceeding one-sixth a span of the longitudinal floor beam measured from a centerline of the potentially failed column. 
 
 
     
     
       2. The method of  claim 1 , wherein the method is applied to one or more potentially failed columns on a same floor or on different floors. 
     
     
       3. The method of  claim 1 , wherein adding a plurality of diagonal top and bottom reinforcing bars within floor slab panels develops self-generated post-tensioning axial compressive forces in the orthogonal floor beams and allows for responsive accommodation of large vertical displacements. 
     
     
       4. The method of  claim 1 , wherein steel bars left over from same construction sites are used as the diagonal top and bottom reinforcing bars. 
     
     
       5. The method of  claim 1 , wherein the plurality of diagonal top and bottom reinforcing bars are embedded within the floor slab thickness of the reinforced concrete floor system. 
     
     
       6. The method of  claim 1 , wherein the plurality of diagonal top and bottom reinforcing bars comprise two sets of diagonal links parallel to each other, wherein the diagonal links comprise top and bottom steel bars embedded within the floor slab thickness. 
     
     
       7. The method of  claim 1 , wherein the added diagonal top and bottom reinforcing bars are single or double links installed within each floor slab panel in the vicinity of the potentially failed column. 
     
     
       8. The method of  claim 1 , wherein the top and bottom steel bars in each floor slab panel provide additional horizontal load paths to increase building redundancy, robustness, ductility, and energy absorption capacity which prevents progressive collapse of the building due to column failure. 
     
     
       9. The method of  claim 1 , wherein the method uses left-over bars or reinforcing bars from a same construction site and does not require external accessories to attach the same to beams, columns, or components of the building.